1. Field of the Invention
The present invention relates to electronic devices including electronic device elements having electrodes provided on opposite major surfaces of the respective electronic device elements. In particular, the present invention relates to an electronic device including an electronic device element supported by being resiliently clamped by resilient contact members that are arranged to individually contact the electrodes.
2. Description of the Related Art
An electronic device related to the present invention is a positive thermistor device. The positive thermistor device is used for limiting electrical current in, for example, a motor driving circuit of a refrigerator, a demagnetizing circuit for a picture tube of a television or a monitor display, and other various uses.
The positive thermistor device includes a positive thermistor element including electrodes provided on respective opposite major surfaces of the positive thermistor element. A resilient contact member resiliently contacts each electrode, whereby the resilient contact member presses the positive thermistor element, thereby supporting the positive thermistor element.
In the positive thermistor device, the positive thermistor element deteriorates according to the condition and environment in which it is used. As a result, the positive thermistor element is abnormally heated, and is sometimes broken.
Electrical current sometimes continues to be applied to the positive thermistor element via the resilient contact members even when the positive thermistor element has been broken, whereby a more serious accident may occur in which a case containing the positive thermistor element is softened, and other defects may occur.
In order to overcome these problems, a structure is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 9-306704, in which when the positive thermistor element is broken, fragments of the positive thermistor element are moved by a spring action of the resilient contact members, thereby opening a circuit and preventing the situation from becoming more serious.
FIGS. 4A and 4B show the structure of the positive thermistor device disclosed in the above Japanese Unexamined Patent Application Publication No. 9-306704.
A positive thermistor element 1 shown in FIG. 4A is has an overall disc-configured configuration. The positive thermistor element 1 is provided with first and second electrodes (not shown) disposed on first and second major surfaces 2 and 3 of the positive thermistor element 1 and oppose each other in the thickness direction thereof.
First and second terminal units 4 and 5 are arranged to clamp the positive thermistor element 1. The first terminal unit 4 includes a first resilient contact member 6, and the second terminal unit 5 includes a second resilient contact member 7.
First and second positioning protrusions 8 and 9 are arranged to clamp the positive thermistor element 1.
The first resilient contact member 6 and the first positioning protrusion 8 contact the first major surface 2 at positions that are separate from each other on the first major surface 2 of the positive thermistor element 1. The second resilient contact member 7 and the second positioning protrusions 9 contact the second major surface 3 at positions that are separate from each other on the second major surface 3. The first resilient contact member 6 resiliently contacts the first electrode on the first major surface 2 so as to be electrically connected to the first electrode. The second resilient contact member 7 resiliently contacts the second electrode on the second major surface 3 so as to be electrically connected to the second electrode.
The first resilient contact member 6 opposes the second positioning protrusion 9 with the positive thermistor element 1 therebetween, the first resilient contact member 6 being positioned toward the periphery of the positive thermistor element 1 from the second positioning protrusion 9. The second resilient contact member 7 opposes the first positioning protrusion 8 with the positive thermistor element 1 therebetween, the second resilient contact member 7 being positioned toward the periphery of the positive thermistor element 1 from the first positioning protrusion 8.
With this arrangement, when the positive thermistor element 1 is broken at a fracture point 10, as schematically shown in FIG. 4A, a fragment 11 moves so as to rotate in a direction along an arrow 13 about a point, at which the fragment 11 is in contact with the second positioning protrusion 9, as a fulcrum and a fragment 12 moves so as to rotate in a direction along an arrow 14 about a point, at which the fragment 12 is in contact with the first positioning protrusion 8, as a fulcrum, as shown in FIG. 4B, since resilient pressing forces of the first and second resilient contact members 6 and 7 are applied to the fragments 11 and 12, respectively, which have been produced by the fracture.
The fragments 11 and 12 move in the directions along the arrows 13 and 14, respectively, thereby interrupting electrical current applied via the positive thermistor element 1 and opening a circuit.
The directions along the arrows 13 and 14 of the movement of the fragments 11 and 12, respectively, shown in FIG. 4B are opposite to each other with respect to the fracture 10. That is, the fragments 11 and 12 move so as to prevent each other from moving in the directions along the arrows 13 and 14, respectively.
Therefore, there is a problem in that even when an accident occurs such that the positive thermistor element 1 is broken, the fragments 11 and 12 sometimes do not sufficiently separate from each other, whereby the circuit does not become open and the electrical current continues to be applied through the broken positive thermistor element 1.
The above-described problems occur not only in the positive thermistor device. The problems may occur in any electronic device in which an electronic component element corresponding to the positive thermistor element is supported, is supplied with electrical current, and is broken due to deterioration in the same manner as the above-described positive thermistor device.
Preferred embodiments of the present invention provide an electronic device in which the above-described problems are overcome.
According to a preferred embodiment of the present invention, an electronic device includes an electronic device element including first and second major surfaces opposing each other in the thickness direction, and first and second electrodes disposed on the first and second major surfaces, respectively, a conductive first resilient contact member and a first positioning protrusion which is not electrically connected to the first resilient contact member, the first resilient contact member and the first positioning protrusion being in contact with the first major surface at respective positions thereof separated from each other, and a conductive second resilient contact member and a second positioning protrusion which is not electrically connected to the second resilient contact member, the second resilient contact member and the second positioning protrusion being in contact with the second major surface at respective positions thereof that are separated from each other. The first resilient contact member and the second resilient contact member are in resilient contact with the first and second electrodes, respectively, so as to be electrically connected thereto.
The first resilient contact member opposes the second positioning protrusion with the electronic device element therebetween, and is positioned toward the periphery of the electronic device element from the second positioning protrusion. The second resilient contact member opposes the first positioning protrusion with the electronic device element therebetween, and is positioned toward an inner portion of the electronic device element from the first positioning protrusion.
The electronic device according to preferred embodiments of the present invention preferably further includes a case for receiving the electronic device element, the first resilient contact member, and the second resilient contact member. The first positioning protrusion and the second positioning protrusion may be provided in the case.
The electronic device according to preferred embodiments of the present invention may include a positive thermistor device which includes a positive thermistor element as an electronic device element.
According to preferred embodiments of the present invention, the first and second resilient contact members and the first and second positioning protrusions resiliently clamp the electronic device element. Only the first and second resilient contact members function as conductors for supplying electrical current. The first resilient contact member opposes the second positioning protrusion with the electronic device element therebetween, and is positioned toward the periphery of the electronic device element from the second positioning protrusion. The second resilient contact member opposes the first positioning protrusion with the electronic device element therebetween, and is positioned toward an inner portion of the electronic device element from the first positioning protrusion. Therefore, fragments produced by fracture of the electronic device element move in the same direction as each other with respect to the position of the fracture by being resiliently pressed by pressing forces of the first and second resilient contact members, whereby the fragments smoothly move, thereby quickly and reliably interrupting electrical current applied via to the electronic device element.
Therefore, a highly safe electronic device is provided.
When the case which is included in the electronic device according to various preferred embodiments of the present invention is made of a resin, and the electronic device element included therein is broken, electrical current is quickly interrupted, and abnormal heat generation is thereby avoided, whereby a risk of entering into an accident mode such as softening of the case can be reliably prevented.